He was rushed to hospital in London for life-saving treatment three days later when he subsequently developed respiratory problems.

The popular GAA player was with four friends when the accident - from which he has now made a full recovery - happened in the Holylands area of Belfast.

The then 19-year-old undergraduate, from near Randalstown, spent 15 days in intensive care and several weeks in hospital before finally being discharged on June 26.

Speaking for the first time about the frightening ordeal, Conleth’s mother Nuala revealed that she was told “several times” that she might lose her youngest child.

“Conleth was taken to St Thomas’ Hospital London after developing breathing problems and he remained in intensive care from May 1 until May 12,” she said.

“He was then brought back to The Royal in Belfast where he spent time in the neural ward and then the brain injury unit at Musgrave before being discharged on June 26.”

She added: “A few times the consltants told us to prepare for the worst. That was awful. But thank goodness we’re on the other side of it.”

Mrs McGrenaghan (52), a nurse, said he was back at Jordanstown University “doing very well” after the accident.

But she recalled how she and her 56-year-old husand John, a retired psychiatric nurse, and their other sons Sean (26), 24-year-old Fergal and daughter Oife (22) kept an anguished vigil by Conleth’s hospital bed, as did his 20-year-old girlfriend Bronagh McGuckin.

“We all went to London to be with him,” she said.

“Miraculously, when he fell, he only ended up with a fractured skull and head injuries.

“The accident came as a great shock but Conleth’s friends dealt with it very well.

“They weren’t with him at the time - they were downstairs - so we don’t know exactly what happened.”

She added: “He has no memories of the accident - the medical staff told us he wouldn’t - and that’s not a bad thing,” she said.

During the family’s dreadful crisis, Conleth’s girfriend’s mother Teresa McGuckin began raising money for them via a ‘GoGetFunding’ page.

Almost £12,000 worth of donations poured in over just a few days and its aim was to help cover expenses.

But Conleth was treated on the NHS and the McGrenaghans, who stayed at the hospital and with friends while in London, didn’t use any of the money.

And, earlier this week, Conleth, now aged 20, presented cheques totalling £11,700 (which remained after the deduction of the fee for using the fundraising website) to two local charities.

“We are giving £10,000 to Brain Injury Matters and £1,700 to the Royal Intensive Care Unit,” Nuala said.

“It’s a family decision and Conleth’s decision to do this because we were so overwhelmed with the support we got from everyone and we were so touched by their generosity and the prayers of the whole community.

“We really wanted to take this opportunity to thank everyone for what they did for us. It was really important to us at a very difficult time in our lives.”